/**
 * Get the first event in a set of event emitters and event pairs.
 *
 * @param {array} stuff
 * @param {function} done
 */
export default function firstEventEmitter(stuff, done) {
  if(!Array.isArray(stuff)) {
    throw new TypeError('arg must be an array of [ee, events...] arrays')
  }

  const cleanups = []

  for(let i = 0; i < stuff.length; i++) {
    const arr = stuff[i]

    if(!Array.isArray(arr) || arr.length < 2) {
      throw new TypeError('each array member must be [ee, events...]')
    }

    const ee = arr[0]

    for(let j = 1; j < arr.length; j++) {
      const event = arr[j]
      const fn = listener(event, callback)

      // listen to the event
      ee.on(event, fn)
      // push this listener to the list of cleanups
      cleanups.push({
        ee: ee,
        event: event,
        fn: fn
      })
    }
  }

  function callback() {
    cleanup()
    done.apply(null, arguments)
  }

  function cleanup() {
    for(let i = 0; i < cleanups.length; i++) {
      const x = cleanups[i]
      x.ee.removeListener(x.event, x.fn)
    }
  }

  function thunk(fn) {
    done = fn
  }

  thunk.cancel = cleanup

  return thunk
}

function listener(event, done) {
  return function onEvent(arg1) {
    const args = new Array(arguments.length)
    const ee = this
    const err = event === 'error' ? arg1 : null

    // copy args to prevent arguments escaping scope
    for(let i = 0; i < args.length; i++) {
      args[i] = arguments[i]
    }

    done(err, ee, event, args)
  }
}
